#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
int feibo(int x)
{
    if (x == 1)
        return 1;
    if (x == 2)
        return 1;
    else return feibo(x - 1) + feibo(x - 2);
}
int main()
{
    int a = 0;
    scanf("%d", &a);
    printf("%d", feibo(a));
    return 0;
}